In recent years, it is known a technology of controlling, by a power management apparatus (for example, HEMS: Home Energy Management System) provided in each consumer, a load provided in a consumer and a dispersed power source provided in a consumer, for example.
Examples of the dispersed power source may include a power generation equipment that utilizes clean energy such as sunlight, wind power, and geothermal energy. Alternatively, examples of the dispersed power source may also include a fuel cell such as SOFC (Solid Oxide Fuel Cell).
In such a system, when it is expected that an amount of power to be supplied from a power grid is smaller than a total amount of power consumed in a consumer connected to the power grid, a power company that manages the power grid transmits, to each power management apparatus, a power curtailment signal (DR: Demand Response) instructing restraint of an amount of power consumed, and each power management apparatus reduces power consumed by a load in response to the power curtailment signal (for example, Patent Literature 1). The power curtailment signal is a signal indicating an amount of power that should be reduced by each consumer (for example, a ratio of power to be reduced relative to power currently consumed, or an absolute value of power to be reduced relative to power currently consumed).